[openstack-dev] [ceilometer] The periodic task on openstack

Bhandaru, Malini K malini.k.bhandaru at intel.com
Sat Nov 17 04:23:25 UTC 2012


One could argue not to adjust next run time after a long run (delayed for whatever reasons).  The argument there being not much may have happened in the interim. In particular you do not want system thrashing.

Ceilometer is not real-time, that is time critical in the sense of flying a plane, breaks on a car.
Best effort for metering purposes, plus host machines come with multiple logical cores, so best effort would be very good. 

For computation purposes to say amount of resources consumed, would be adequate to maintain last run time.
 (current-time - last-run-time).
In the case of processing log files, the log entries would have their own time stamps, to determine from where to continue processing.

Malini


-----Original Message-----
From: Jiang, Yunhong [mailto:yunhong.jiang at intel.com] 
Sent: Friday, November 16, 2012 6:45 PM
To: OpenStack Development Mailing List
Subject: Re: [openstack-dev] [ceilometer] The periodic task on openstack

> > Its almost as if we'd want the standard libs to be unmonkey-patched 
> > when executing on real threads so as to avoid needlessly yielding 
> > and hence chewing up more elapsed time to task completion (if that 
> > makes any sense ...).
> 
> That's a good question.  Eventlet provides a threadpool implementation 
> that we could use for this, so if going that route I think it's all good.
> 
> http://eventlet.net/doc/threading.html#tpool-simple-thread-pool

According to the doc, "A key restriction is that the object's methods should not switch greenlets or use Eventlet primitives, since they are in a different thread from the main hub, and therefore might behave unexpectedly" and I assume this should apply to the eventlet.tpool.execute() also?

--jyh

> 
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> Russell Bryant
> 
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